A po face is necessary

Interesting. That's not quite what the Forest says:

http://humanities.byu.edu/rhetoric/Figures/A/apophasis.htm

AHD4, on the other hand:

http://www.bartleby.com/61/7/A0370700.html

The Forest seems to think it's more of a slightly expanded form of paralipsis.

http://humanities.byu.edu/rhetoric/Figures/P/paralipsis.htm